The present disclosure relates to an electrical switch. More specifically, the present disclosure relates to a thin electrical switch used in electrical appliances such as portable telephones, digital cameras, and other similar types of mobile or portable products in which the miniaturization of the components is a significant parameter in the design and production.
In conventional designs, a thin electrical switch typically has a domed triggering member in the form of a spherical cap. An abrupt change of state of the triggering member provides a user with a tactile sensation indicated the state change. The electrical switch also typically includes a bottom contact plate, or base, which is produced by over-molding a material, such as plastic, to delimit a recess which receives the elastically deformable triggering dome.
In a typical design, such as the design illustrated in U.S. Pat. No. 6,946,610, the content of which is hereby incorporated by reference in its entirety, when seeking to reduce the dimensions and, in particular, the thickness of the over-molded plastic material, the arrangement of components results such that when a force is applied to provoke the triggering, and subsequent state change of the switch, various metallic parts and the over-molded plastic components may separate by delamination, leading to a potential failure of the switch.
To reduce the dimensions and the thickness of a switch, it is possible to produce the switch in association with a bottom plate including one or more printed circuits, thereby reducing the number and size of individual components within the switch. The triggering member dome is placed directly in contact with a conductive track or conductive tracks on the print circuit as is illustrated, for example, in U.S. Pat. No. 7,378,609, the content of which is hereby incorporated by reference in its entirety. However, as the thickness of the bottom plate is reduced, it becomes flexible. For optimum performance, the triggering member, by its circular bottom edge, should be bearing on a perfectly flat surface in order to operate reliably and sustainably. If the bottom plate flexes in response to a force being applied to the triggering member, the triggering member may not completely contact the conductive tracks. Additionally, this solution is costly because it does not allow for the implementation of a mass production line manufacturing method.
U.S. Pat. No. 7,589,607, the content of which is hereby incorporated by reference in its entirety, proposes a structure in which the domed triggering member, having small dimensions, is linked by a tab to a surrounding metal plate. Such an arrangement is not practical or satisfactory for a majority of applications as the domed triggering member does not freely move and the life of the switch is particularly reduced.